WASHINGTON (CNN) -- Saddam Hussein did not possess stockpiles of illicit weapons at the time of the U.S. invasion in March 2003 and had not begun any program to produce them, a CIA report concludes.

In fact, the long-awaited report, authored by Charles Duelfer, who advises the director of central intelligence on Iraqi weapons, says Iraq's WMD program was essentially destroyed in 1991 and Saddam ended Iraq's nuclear program after the 1991 Gulf War.

The Iraq Survey Group report, released Wednesday, is 1,200 to 1,500 pages long.

The massive report does say, however, that Iraq worked hard to cheat on United Nations-imposed sanctions and retain the capability to resume production of weapons of mass destruction at some time in the future.

"[Saddam] wanted to end sanctions while preserving the capability to reconstitute his weapons of mass destruction when sanctions were lifted," a summary of the report says.

Duelfer, testifying at a Senate hearing on the report, said his account attempts to describe Iraq's weapons programs "not in isolation but in the context of the aims and objectives of the regime that created and used them."

"I also have insisted that the report include as much basic data as reasonable and that it be unclassified, since the tragedy that has been Iraq has exacted such a huge cost for so many for so long," Duelfer said.

The report was released nearly two years ago to the day that President Bush strode onto a stage in Cincinnati and told the audience that Saddam Hussein's Iraq "possesses and produces chemical and biological weapons" and "is seeking nuclear weapons."

"The danger is already significant and it only grows worse with time," Bush said in the speech delivered October 7, 2002. "If we know Saddam Hussein has dangerous weapons today -- and we do -- does it make any sense for the world to wait to confront him as he grows even stronger and develops even more dangerous weapons?"

Speaking on the campaign trail in Pennsylvania, Bush maintained Wednesday that the war was the right thing to do and that Iraq stood out as a place where terrorists might get weapons of mass destruction.

"There was a risk, a real risk, that Saddam Hussein would pass weapons or materials or information to terrorist networks, and in the world after September the 11th, that was a risk we could not afford to take," Bush said.

But Sen. Jay Rockefeller of West Virginia, the top Democrat on the Senate Intelligence Committee, seized on the report as political ammunition against the Bush administration.

"Despite the efforts to focus on Saddam's desires and intentions, the bottom line is Iraq did not have either weapon stockpiles or active production capabilities at the time of the war," Rockefeller said in a press release.

"The report does further document Saddam's attempts to deceive the world and get out from under the sanctions, but the fact remains, the sanctions combined with inspections were working and Saddam was restrained."

But British Prime Minister Tony Blair had just the opposite take on the information in the report, saying it demonstrated the U.N. sanctions were not working and Saddam was "doing his best" to get around them.

He said the report made clear that there was "every intention" on Saddam's part to develop WMD and he "never had any intention of complying with U.N. resolutions."

At a hearing of the Senate Armed Services Committee Wednesday, panel Chairman John Warner, R-Virginia, called the findings "significant."

"While the ISG has not found stockpiles of WMD, the ISG and other coalition elements have developed a body of fact that shows that Saddam Hussein had, first, the strategic intention to continue to pursue WMD capabilities; two, created ambiguity about his WMD capabilities that he used to extract concessions in the international world of disclosure and discussion and negotiation.

"He used it as a bargaining tactic and as a strategic deterrent against his neighbors and others."

"As we speak, over 1,700 individuals -- military and civilian -- are in Iraq and Qatar, continuing to search for facts about Iraq's WMD programs," Warner said.

But Sen. Carl Levin of Michigan, ranking Democrat on the committee, said 1,750 experts have visited 1,200 potential WMD sites and have come up empty-handed.

"It is important to emphasize that central fact because the administration's case for going to war against Iraq rested on the twin arguments that Saddam Hussein had existing stockpiles of weapons of mass destruction and that he might give weapons of mass destruction to al Qaeda to attack us -- as al Qaeda had attacked us on 9/11," Levin said.

Sen. Edward Kennedy, D-Massachusetts, asked Duelfer about the future likelihood of finding weapons of mass destruction, to which Duelfer replied, "The chance of finding a significant stockpile is less than 5 percent."

Based in part on interviews with Saddam, the report concludes that the deposed Iraqi president wanted to acquire weapons of mass destruction because he believed they kept the United States from going all the way to Baghdad during the first Gulf War and stopped an Iranian ground offensive during the Iran-Iraq War in the 1980s, senior administration officials said.

U.S. officials said the Duelfer report is "comprehensive," but they are not calling it a "final report" because there are still some loose ends to tie up.

One outstanding issue, an official said, is whether Iraq shipped any stockpiles of weapons outside of the country. Another issue, he said, is mobile biological weapons labs, a matter on which he said "there is still useful work to do."

Duelfer said Wednesday his teams found no evidence of a mobile biological weapons capability.

The U.S. official said he believes Saddam decided to give up his weapons in 1991, but tried to conceal his nuclear and biological programs for as long as possible. Then in 1995, when his son-in-law Hussain Kamal defected with information about the programs, he gave those up, too.

Iraq's nuclear program, which in 1991 was well-advanced, "was decaying" by 2001, the official said, to the point where Iraq was -- if it even could restart the program -- "many years from a bomb."